This invention relates to power supply apparatus of the converter type, in which output power is obtained by means of an oscillating circuit. The circuit is powered from the input power to be converted and an alternating output is obtained from the oscillatory current of the stage. Such units are convenient for use where it is desired to operate relatively low voltage equipment for an alternating mains supply. The invention has for its object to provide converters which are improved in various respects, as will appear.
A known type of converter power supply apparatus includes oscillator circuit comprising a transformer and two semi-conductor switching devices arranged to be alternately switched to produce a.c. load current through the primary of the transformer, the secondary winding of the transformer providing control current to the switching devices in such a manner as to ensure a constant relation between control and load currents.